Treatment of manganese alloys



- alloy would be 0.27%.

Patented Nov. 12, 1940- UNITED STATES PATENT OFFICE 2,221,625 TREATMENT OF MANGANESE ALLOYS No Drawing. Application February 20, 1939,

Serial No. 257,456

* 8 Claims. (Cl. -80) This invention relates to the treatment of manganese alloys and is particularly concerned with the removal of sulphur therefrom in order to provide alloys essentially free of sulphur.

The presence of sulphur inmanganese alloys and manganese base alloys is most likely to occur, by virtue of the employment of electrolytic manganese as a constituent of such alloys.' Electrolytic manganese, as prepared in accordance with I the process disclosed in U. S. Patent No. 2,119,560,

for example, contains in the neighborhood of 0.2% to 0.3% sulphur. The ultimate presence of sulphur in certain manganese alloys, among which are particularly alloys containing upwards of 30% manganese and as high as about 97% manganese, has been found to be particularly objectionable in that it renders treatment, working or fabricating operations impossible as well as deleteriously affecting various properties and characteristics of said alloys. While, in many instances, itis of advantage to remove the sulphur from the electrolytic manganese prior to alloying the manganese with such other elements as may comprise the alloys, there are occasions when it may be preferable initially to form the manganese alloy' from the electrolytic manganese containing the aforementioned amounts of sulphur and then to treat the resulting alloy to effect desulphurization.

It will be clear that if electrolytic manganese containing 0.3% sulphur is employed in-an'alloy containing-say 40% of manganese, the sulphur content of the finished alloy will be 0.12% assuming that sulphur has not been introduced into the alloy from any othertsource. If, however, the manganese content of the alloy is say then the sulphur content of thefinished In the usual case, the sulphur content of the alloys should be reduced to not substantially in excess of 0.02% and should preferably be substantially less than that or in other words of the order of a few thousandths of a percent.

In accordance with my present invention, the sulphur, however it may have been'introduced into the manganese alloys, is efiectively removed in a simple and inexpensive manner.

In general, the removal of the sulphur from the manganese alloys containing the same is effected by mixing the latter, in the molten state, with an acidic oxide or a salt, particularly an alkali metal salt, formed therefrom or slabs containing the same. This treatment efiectively removes the sulphur but introduces an element of the acidic oxide or the likehinto the alloy. The latter. is

then treated, in a molten condition, with an oxide of manganese, particularly manganese dioxide. In this manner, the introduced element may be removed to such an extent that, in many cases, it is below the point of accurate analytical 5 determination- The result is the preparation of a substantially sulphur-free manganese alloy; In those cases where the introduced element is not a deleterious constituent of the alloy, it may be permitted to remain in the alloy and the sub- 10 sequent step of treatment with manganese oxides may be eliminated. Indeed, in certain alloys, the presence of small amounts of such introduced elements is highly desirable. The present invention enables the production of such 5 alloys simultaneously with the efiective reduction or substantial elimination of sulphur therefrom.

The acidic oxides or salts formed therefrom which I employ for the sulphur removal treat- 20 ment may be selected from a group which includes, for example, silica, titania, vanadium oxides, phosphorus. pentoxide, alkali metal pyrophosphates, and the like. The sulphur is removed in the form of a gas, namely, sulphur di- 25 oxide.

The reaction of the sulphur-containing manganese alloy with the acidic oxide or compound thereof is not a surface reaction but'the acidic oxide or compound thereof, as the case may be, 30 appears to disperse or dissolve in the molten manganese alloy and is apparently in equilibrium with the dispersed or dissolved manganese or other sulphide present in the manganese alloy. As a result, a substantial, though minor, 35 amount of acidic oxide or compound thereof must be added in some cases to obtain effective desulphurlzation. It should be understood that I do not wish to be limited by what the exact mechanlsm of the reaction may be since the in- 40 vention is predicated upon discoveries and results (a) 100 pounds of an alloy, comprising 20% nickel, 30% copper and 50% of electrolytic man- 56 ganese containing 0.2 5% sulphur (the sulphur content based on the alloy as a whole being 0.125%), are melted in a high frequency induction furnace at a temperature between 1300 degrees C. and 1400 degrees C. To the molten alloy, maintained at the indicated temperature, 8 pounds of silica are'added. The stirring which is produced by the high frequency current is allowed to pi oceed for 15 to 20 minutes. The silica is then removed as completely as possible from the melt.

(b) The manganese alloy, containing several tenths of one percent of silicon, which is produced in part (a) hereinabove, is mixed, in the molten state, at a temperature of about 1400 degrees C. with 2 pounds of manganese dioxide, the mass being maintained at a temperature of 1400 degrees C. to 1500 degrees C. for between 5 and 15 minutes. The manganese oxide slag is then removed and the metal cast into ingots. On analysis, the resulting manganese alloy contains 005% sulphur and .03% silicon.

Example II (a) 100 pounds of an alloy, comprising 15% chromium, 48% iron and 37% electrolytic manganese containing 0.28% sulphur ,(the sulphur content based on the alloy as a whole being about 0.10%), are melted in a high frequency induction furnace at a temperature between 1500 degrees C. and 1550 degrees C. To the molten alloy, maintained at such temperature, 5 pounds of sodium pyrophosphate are added. The reaction is allowed to proceed for 10 to 20 minutes. The sodium pyrophosphate is then removed as completely as possible from the melt.

(b) The manganese alloy, containing several tenths of one percent of phosphorus which is produced in part (a) of this example, is mixed, in the molten state, at a temperature of about 1500 degrees C., with 2 pounds of manganese dioxide, the mass being maintained at a temperature of 1500 degrees C. to 1600 degrees C. for between 10 and 20 minutes. The manganese oxide slag is then removed and the metal cast into ingots. On analysis, the resulting manganese alloy contains .005% sulphur and .035% phosphorus.

Example III (a) 100 pounds of an alloy, comprising 10% copper and electrolytic manganese containing 0.24% sulphur (the sulphur content based on the alloy as a whole being about 0.21%), are melted as described in the previous examples at a temperature between 1300 degrees C. and 1400 degrees C. To the molten alloy, maintained at the indicated temperature, 5 to 6 pounds of titania are added and the reaction'is allowed to proceed for from 10 to 20 minutes. The titania is then removed as completely as possible from the melt.

(b) The manganese alloy, containing several tenths of one percent of titanium, which is produced in part (a) of this example, is mixed, in the molten state, at a temperature of about 1400 degrees C. with 5 pounds of manganese dioxide, the mass being maintained at a temperature of 1400 degrees C. to 1500 degrees C. for between 10 and 20 minutes. The manganese oxide slag is then removed and the metal cast into ingots. On analysis, the resulting manganese alloy contains .003% sulphur and .02% titanium.

' While the practice of the invention is illustrated in the above examples with respect to certain alloys, it has utility in connection with the treatment of all manganese-base alloys, par.- ticularly those having a manganese content in excess of 30%. The alloys may contain one or more of the elements nickel, copper, iron, carbon, zinc, vanadium, chromium, tungsten, molybdenum, tin, aluminum, beryllium, silver, magnesium, and/or other elements in varying amounts, some from a fraction of one percent to several percent and others as high as about 70%.

The melting of the maganese alloys is preferably carried out in a highly dense alumina crucible although magnesia crucibles may be used in certain cases.

The proportions of acidic oxides or compounds thereof and oxides of manganese are subject to relatively wide variations. The proportions utilized depend, among other things, on the amount of sulphur present and the amount of the element such as silicon, phosphorus, titanium or the like introduced into the manganese alloy, it being understood that the smaller the percentage of sulphur and silicon or the like the less acidic oxides and oxides of manganese, respectively, will be required. In the average case, from 5% to 10% of acidic oxide or the like and from 1% to 4% of a manganese oxide, based on the weight of the manganese alloy, will be suflicient to achieve the desired results.

The temperature at which the manganese a1- loys and acidic oxide or the like and the oxides of manganese, respectively, are mixed is variable. It should not be so high as to cause undesired volatilization. About 1300 degrees C. to 1600 degrees C. represents a preferred working range, although, of course, the temperature employed will depend upon the nature of the manganese alloy and the nature of. the acidic oxide or compound thereof or oxide of manganese, as the case may be. In general, a satisfactory range is from 50 degrees C. to degrees C. above the melting point of the manganese alloy.

It is frequently advantageous, in carrying out the step of removing the introduced silicon or the like, to mix the oxide of manganese with a small amount of a fiuxing material such as sodium carbonate, calcium carbonate or calcium fluoride. A good fiuxing material may be prepared'from approximately equal parts of sodium carbonate, calcium carbonate and calcium fluoride. In general, however, fairly satisfactory results are obtained without resorting to such practice.

Unless otherwise specifically stated, the term acidic oxide as employed in the claims,.will be understood to cover not only the oxides as such but also salts containing the same such as alkali metal silicates, alkali metal phosphates, and the like.

What I claim as new and'desire to protect by Letters Patent of the United States is:

1. The method of substantially reducing the sulphur content of a manganese alloy contain-v 2. The method of substantially reducing the sulphur content of a manganese alloy containing at least 30% -of manganese which comprises contacting said manganese alloy, in molten condition, with an acidic oxide for a period of time sufiicient to eifect the desired removal of the sulphur, whereby an element of said acidic oxide is introduced into the manganese alloy, and then mixing the resulting manganese alloy, in molten condition, with an oxide of manganese for a period of time suflicient to effect the desired removal of said introduced element.

3. The method of substantially reducing the sulphur content of a manganese alloy containing at least 30% manganese and simultaneously introducing an element derived from an acidic oxide which comprises agitating said manganese alloy, in a molten condition, with an acidic oxide for a period oi time sumc'ient to efiect the desired removal of the sulphur.

4. The method of reducing the sulphur content of a manganese alloy, containing at least.

30% manganese, from approximately 0.2% or more to approximately 0.02% or less which comprises melting said manganese alloy and mixing the same, while in molten condition, with silica.

5. The method of substantially reducing the sulphur content of a manganese alloy containing the same which comprises contacting said alloy, in molten condition, with from about to about of an alkali metal phosphate for a period of time suificient to effect the desired comprises agitating said manganese alloy, at a temperature about 50 degrees C. or more above its melting point, with silica for a period of time suflicient to effect the desired removal of the sulphur.

7. The method of substantially reducing the sulphur content of manganese alloys prepared from electrolytic manganese which comprises agitating said manganese alloys, in a molten condition, with an alkali metal silicate for a. period of time sumcient to effect the desired removal of the sulphur. I

8. In a method of producing a substantially sulphur-free manganese alloy from an alloy prepared from electrolytic manganese, said alloy initially'containlng at least 0.05% sulphur, which comprises agitating said manganese alloy, in a molten condition, with an acidic oxide for a period of time suillcient to effect the desired removal of the sulphur.

C. TRAVIS ANDERSON. 

